FIELD OF THE INVENTION
The invention relates to a method for testing pipes, particularly in heat exchangers of nuclear plants, by means of eddy current where several measurements with different frequencies are made and the measuring results are interlinked with each other for suppressing design-related interference influences.
Among the design-related interference influences which have an adverse effect on the determination of defects in that they cause signals similar to faults, are counted spacers, ovalness at the beginning of a pipe elbow, deposits, the tube elbow, rolled-in portions, external baffles and flow distribution plates, etc. The interference of the tubes and components are dependent on frequency. To eliminate the influences of the interference signals, the measurements and tests are performed in sequence one after the other with different frequencies. In this way the interference signals are in the background compared to the defect signals. However, the parameters of such multiple-frequency interlinkage must be adapted to the interference signal to be suppressed. If different interference influences are present in the region to be tested, interlinkages with different sets of parameters must as a rule be used for suppressing them. The problem then consists in selecting the respectively correct set of parameters for the different interference signals which occur in the testing of a pipe sequentially in time.